Ultrafast time-resolved coherent degenerate four-wave-mixing spectroscopy for investigating molecular dynamics in different states

In this paper, ultrafast time-resolved coherent degenerate four-wave-mixing (DFWM) spectroscopy is performed to investigate molecular dynamics in the gaseous phase. Laser pulses lasting for 40 fs are used to create and monitor different vibrational eigenstates of iodine at room temperature (corresponding to a low saturation pressure of about 35 Pa). Using an internal time delay in the DFWM process resonant with the transition between the ground X-state and the excited B-state, the vibrational states of both the electronically excited and the ground states are detected as oscillations in the DFWM transient signal. The dynamics of either the electronically excited or ground state of iodine molecules obtained are consistent with the previous high temperature studies on the femtosecond time-resolved DWFM spectroscopy.

► We investigated the iodine molecular dynamics in different states at room temperature.
► We used an internal time delay in the DFWM process resonant with the transition between the ground X-state and the excited B-state.
► Increasing DWFM signal will increase signal-to-noise ratio.
► Decreasing iodine vapor pressure will decrease various cross terms and interferences.
► Environmental and atmospheric measurements depend on the low-concentration monitor technique about real-time detection.